Abstract: Disclosed is a method for forming a solid state electrolyte. The method includes a first step of combining a solid comprising lithium, a second solid comprising lanthanum, a third solid comprising zirconium, and a fourth solid comprising bismuth to form a mixture. The method includes a second step of applying simultaneous heat and pressure to the mixture to form a ceramic material. The solid state electrolyte is ionically conducting and can be used as an electrolyte for an electrochemical device such as a battery or supercapacitor.